Small form factor pluggable optical transceivers (“SFPs”) are known in the art. Typically, such transceivers consist of an elongated module with at least optical two ports, one for receiving light pulses and another for transmitting light pulses to a remote location. Such devices also typically include an electrical interface. Examples of such devices are disclosed in U.S. Pat. Nos. 7,314,384, and 7,186,134.
These SFP modules typically plug into a shelf or chassis to be used in an optical switch or router. Such modules often include fingerstock that extend outwardly and upwardly from the device in a manner that leaves the end of the fingers not in contact with the SFP. The ends of the fingers resiliently press the rack or chassis and serve to connect the outside of the SFP module to the chassis. One such finger is shown in FIG. 1, which depicts the open end 101 of a finger for resiliently pressing against a chassis, and a length 102 of the finger that extends along the outside surface of the SFP module. The length 102 of the finger is shown extremely magnified.
One problem is that the point of contact between each finger and the SFP housing is somewhat undefined. Among numerous fingers for a particular SFP module, there may be different contact points. This is due largely to imperfections in the outside surface of the SFP module and the bottom surfaces of the fingers, as depicted in FIG. 1. The point of actual contact between each finger and the surface of the SFP module is thus less than exact.
The distance between the end of the finger that resiliently presses against the chassis, to the part of the finger that contacts the outer surface of the SFP module, represents a source of EMI leakage. Because of the variability of this distance among the plural fingers for a particular SFP module, in some cases, this distance may be longer than the wavelength of signal which represents the EMI (Electromagnetic Interference). This means the gap under the finger permits EMI interference to pass. This problem is particularly acute in relatively high frequency systems, wherein the wavelengths of interest are relatively short.
Another problem with prior art arrangements such as that shown in FIG. 1 is that the modules are typically built from the upper and lower housing, shown as 112 and 114 in FIG. 1. Because the seal 113 is never exactly perfect, gaps are left which also provide for EMI leakage.
A still further problem relates to the latch used to maintain the SFP module in the chassis in which it is typically installed. More specifically, there is often a slidable latch or similar type mechanism that clips the SFP into the chassis. However, this movable part also presents a source of EMI leakage because the EMI signals may leak in around the slidable part.
In view of the foregoing, there exists a need in the art for a more effectively sealed module in order to prevent EMI leakage.